The invention relates to a system for cooling to a low temperature at least one piece of equipment, particularly a piece of motor vehicle equipment, comprising a circulation loop for heat-transfer fluid on which loop are mounted a low-temperature heat exchanger and at least an equipment exchanger comprising a heat-exchange surface. It also relates to a low-temperature heat exchanger and to an equipment exchanger that form part of the cooling system of the invention.
Present-day motor vehicles comprise an increasingly high number of pieces of equipment which exchange heat with their external surroundings. Some of these pieces of equipment need to be heated up, for example the fuel heater. However, most of these pieces of equipment need to be cooled. This is the case, in particular, of the condenser which forms part of the motor vehicle cabin air-conditioning circuit, and is also true of the oil cooling radiator and the intercooler radiator. Increasingly often, also, the exhaust gases are cooled in order to reduce pollution.
Some of these pieces of equipment, such as the oil cooling radiator or the radiator that cools the exhaust gases, do not need to be cooled to a low temperature. They can therefore be placed without disadvantage in the cooling circuit of the vehicle combustion engine through which circuit there circulates a heat-transfer fluid the temperature of which generally ranges between 85° C. and 100° C. However, other pieces of equipment need to operate at the lowest possible temperature so as to improve their efficiency. This is the case in particular of the condenser of the air-conditioning circuit and the intercooler.
This is why provision is made for currently known vehicles to be equipped with a low-temperature cooling circuit through which a heat-transfer fluid circulates at a temperature below that of the high-temperature circuit. The condenser of the air-conditioning circuit or the intercooler may thus be cooled more effectively down to a lower temperature.
However, in currently known vehicles, the low-temperature cooling circuit is equipped with a low-temperature heat exchanger which has just one inlet nozzle and just one outlet nozzle, the heat-transfer fluid circulating in one or several passes. The low-temperature heat exchanger delivers just one temperature level and the fluid that is to be cooled, for example the air in the intercooler, is cooled to just one level of heat exchange.
In currently known vehicles, the coolant fluid is condensed by the ambient air but it is possible, by using a low-temperature circuit, to condense it using the same heat-transfer fluid as is used to cool the engine.
The cooling of these fluids is therefore often insufficient to guarantee an optimum reduction in temperature. For example, the temperature of the charge air is too high on the intake side at critical points in the event of high load on the engine, or alternatively the condensation of the coolant fluid is insufficient, which results in degraded performance of the air-conditioning circuit.